Apparatus and method for cooling a crimped tow

ABSTRACT

A tow of synthetic filaments is cooled with an apparatus comprising a cooling element comprising first and second sections and means for contacting said tow with a cooling fluid in said second section, said first section having a surface extending a distance and positioned for receiving said tow and said second section having a surface extending a distance outwardly from said first section.

United States Patent Erickson et a1.

APPARATUS AND METHOD FOR COOLING A CRIMPED TOW Inventors: Wayne K. Erickson; Albert F.

Stegelman, both of Greenville, SC.

Phillips Petroleum Company, Bartlesville, Okla.

Filed: Sept. 14, 1973 Appl. No.: 397,259

Assignee:

US. Cl 28/l.6; 28/7214 Int. Cl D02g 1/12 Field of Search 28/1.6, 1.7, 72.12, 72.14

References Cited UNITED STATES PATENTS 11/1961 Becker ct al 28/7214 X June 10, 1975 3,041,705 7/1962 Sonnino 28/L6 3,108,352 10/1963 Haigier ct a1. 28/1.6 3,636,149 1/1972 Tambini 28/1] X 3,703,753 11/1972 Binfordm. 28/7112 3,808,654 5/1974 Stanley 28/7214 Primary Examiner-Louis K. Rimrodt [57] ABSTRACT A tow of synthetic filaments is cooled with an apparatus comprising a cooling element comprising first and second sections and means for contacting said tow with a cooling fluid in said second section, said first section having a surface extending a distance and positioned for receiving said tow and said second section having a surface extending a distance outwardly from said first section.

12 Claims, 1 Drawing Figure Gum.

APPARATUS AND METHOD FOR COOLING A CRIMPED TOW BACKGROUND OF THE INVENTION The invention relates to a method and apparatus for processing a tow of synthetic filaments.

Synthetic filaments are frequently gathered to form a tow before processing. The processing often includes a drawing step unless previously drawn filaments are used. Also, the tow is generally heated and crimped by various methods as known in the art. After the tow is crimped, it is either cut into staple or packaged as crimped continuous filament yarn. Some examples of such filaments include the groups of polyarnides, polyesters, and polyolefins. These and other similar filaments are used for various purposes, some of which include carpet, apparel, nonwoven fabrics, such as carpet backing and fiberfill products for pillow filling, furniture upholstering, lining sleeping bags, etc. In these and other products, crimp and crimp retention is very important in that it directly affects the bulk and feel of the filaments and thus the quality of the final product. Some of the various bulked fibers have been very successful commercially; however, others have not. It is generally agreed that improved bulk is desirable for most applications and in some cases it is essential for commercialization.

It is an object of the invention to provide a method and apparatus for processing a tow of synthetic filaments.

Another object of the invention is to provide a method and apparatus for cooling a tow of synthetic filaments.

It is a further object of the invention to provide a method and apparatus for increasing the crimp and crimp retention of crimped synthetic filaments.

SUMMARY OF THE INVENTION According to the invention, a tow of synthetic filaments is cooled by passing a tow of heated crimped filaments into a first zone wherein the movement of said tow is restricted and said tow is cooled by natural convection while experiencing near zero tension, subsequently passing said tow to a second zone wherein said tow is cooled by forced convection by contacting said tow with a cooling fluid while said tow is experiencing tension sufficient to elongate said crimped tow but not to remove the crimp in said tow and sensing and controlling the crimped tow inventory in said first zone.

Further according to the invention, apparatus for cooling a tow of synthetic filaments comprises a cooling element comprising first and second sections and a means for contacting said tow with a cooling fluid in said second section, the first section of said cooling element having a surface extending a distance and positioned for receiving said tow and the second section of said cooling element having a surface extending outwardly from said first section.

DETAILED DESCRIPTION OF THE INVENTION Referring to the attached drawing, the invention will be more fully described. A tow of synthetic filaments is fed to a crimping means such as stuffer crimper 22 via nip rolls 24 driven by power means 25. The tow is heated in the crimping means with steam or other suitable fluid via line 26; however, the tow 20 can be heated prior to entering nip rolls 24 by various methods known in the art. Although a stuffer crimper 22 is shown, other crimping means for crimping a tow can be used. The invention is in the method and apparatus used to cool the tow after crimping and not in the method or apparatus used to crimp the tow. The tow exiting the crimper 22 in the form of a plug of crimped tow at point 28 enters the first section 30a of the cooling element, which is essentially a trough-like structure generally designated by reference numeral 30. The tow 20 in the first section 30a is prevented from buckling by a weight means 32. The weight means 32 also provides sufficient back pressure to the crimping means to preclude upset; this is, where the plug is blown out of the crimping means interrupting continuous crimping action.

The weight means 32 is shown as being a rectangular tray having a curved front portion. The weight means 32 can be adjusted by placing different weights 35 in the tray to vary the force pressing the tow against the surface of the first section 300 and thus providing back pressure for the crimping means and/or preventing the tow from buckling in said section. Slots 33 in the first section 30a are provided to accept pins 31 attached to weight means 32 in order to fix only the horizontal position of weight means 32. Alternately, a cylindrical weight can be used rather than a tray as shown in the attached drawing, but the tray is preferred because of the ease in making weight adjustments.

The tow 20 in the first section 30a experiences little or no tension since the tow is pushed rather than pulled. If any tension were applied to the tow at this point, it would reduce both crimp and crimp retention, because the tow is hot; however, it is below the melt temperature of the filaments. The cooling that takes place in the first section 30a is primarily by natural convection as other methods of transferring heat generally require at least some tension be applied to the tow. The first section should be long enough to permit the tow to cool to a temperature where moderate tension can be applied to the tow in the second section 30b without impairing the crimp or crimp retention. Generally, for most filaments, a tow residence time is in the range of from about 5 to 20 seconds. By tow residence time is meant the time it takes for any one point on the tow to pass from the entrance to the exit of the particular section of the apparatus designated. The temperature of the tow leaving the first section can vary widely depending upon the tow material being processed, but for polyolefins, polyesters and polyarnides the temperature is generally in the range of from about to 250F.

It is desirable to use a suitable sensing means 34, such as a photoelectric device or electric eye located near the junction of said first and second sections to sense the end of the tow plug 38. Most tow crimping means form a tow plug which is well known to those skilled in the art. The end of the tow plug 38 is detected by the sensing means 34 which indicates that the tow inventory or accumulation in the first section 30a is at a maximum. The sensing means 34 functions in conjunction with the withdrawal means 36. A suitable withdrawal means 36, such as nip rolls driven by power means 37, pulls the tow through the second section 30b of the cooling element 30. The power means 37 generally as two speeds, one for pulling the tow 20 faster than said tow accumulates in said first section and the other for pulling the tow 20 slower than said tow accumulates in said first section. The faster speed of the power means 37 is used when the sensing means 34 detects the end of the tow plug. When the sensing means 34 does not detect the end of the tow plug 38, indicating the tow inventory in the first section 30a is less than the maximum, the slower speed of the power means 37 is used and thus allows the tow plug 38 to accumulate in the first section 300.

The tow in the second section 30b is primarily cooled by forced convection as contrasted with cooling by natural convection in the first section 30a. Air or other suitable fluid is forced over and through the tow by a contacting means 40, such as air knives. An air knife is an enclosed longitudinal chamber in which a narrow slit is out along the length of the chamber. The air knife is positioned across and above the tow. The slit is pointed downward so that when a source of cooling fluid 42, such as air, is piped 44 to the air knife, the cooling fluid 46 is forced downward against and through the tow. The air knives tend to open or separate the tow which also facilitates cooling. The number of air knives needed to sufficiently cool the tow will vary with the particular process involved. Normally from 2 to 6 air knives are required, but as few as one or as many as 12 can be used depending upon the requirements of the tow to be cooled.

The length of the second section 30b is not critical with regard to tow residence time but it should be long enough to cool the tow substantially to ambient temperature. The second section supports the tow 20 under the air knives which are normally spaced apart in the range offrom about 1 to 6 inches to promote efficient utilization of the cooling fluid. In addition, it is desirable to allow some space between the entrance of the second section 30b and the first air knife in said section. This additional space allows the crimped tow to become elongated before the tow is contacted with the cooling fluid which also promotes efficient use of the cooling fluid. Generally, the supply of cooling fluid, such as compressed air, is limited and should be used efficiently.

[t is desirable for the second section 301) to be perforated to enable cooling fluid 46 to escape after passing through the tow. These perforations 50 are very effective in improving the overall efficiency of the second section 30b.

Where air knives are used as the contacting means 40, the air pressure is in the range of from about 40 to 60 psig, depending upon the distance between the air knives and the tow. The flow of air should be great enough to adequately cool the tow, but not so great as to whip the tow about excessively.

It is important to emphasize that by utilizing the present invention negligible tension is applied to the tow 20, in the first section 300, since the tow 20 is being pushed by nip rolls 24 rather than pulled by the withdrawal means 36 as is the tow 20 in the second section 30!). Also by the time the tow enters the second section, it is cool enough that the tension applied to the tow by the withdrawal means 36 will not impair the crimp and crimp retention of the tow. Normally, the withdrawal means 36 applies tension to the tow in the second section 30b sufficient to elongate the crimped tow without removing the crimp in the tow.

The legs 52 are adjustable so that the cooling element 30 can be raised or lowered. This is helpful to eliminate buckling of the tow in the first section 30a. It has been found that if buckling does occur, that lowering the discharge end 54 of the cooling element 30 will normally correct the problem.

By the time the tow 20 leaves the second section, the temperature of the tow 20 is near ambient temperature which is generally in the range of from about to l40F and the tow can withstand considerable tension without damage to crimp and crimp retention. This is important because the tow is usually subjected to considerable tension during the final steps of processing such as when it is cut into staple or packaged as continuous filament yarn.

EXAMPLE Polypropylene filaments were used to form a tow approximately 4 inches wide having a denier of 520,000 which was passed through a stuffer box crimper maintained under 5 psig steam resulting in a heated tow plug. This plug was cooled in an apparatus according to the present invention.

The first section of the cooling element was 48 inches long, 5% inches wide and had sidewalls 3 inches high. The weight means was a tray 10 inches long and 4 inches wide with a curved front portion. Pins were attached toward the front portion of the tray extending outwardly and riding in vertical slots in the sidewalls of the first section in order to restrict horizontal movement of the tray but to allow free vertical movement. The weight of the tray and weights used therein was approximately two pounds. The first section provided a 12-15 second residence time and cooled the tow from approximately 2l2F to approximately 190F.

The second section of the cooling element was 36 inches long, 5% inches wide and had 3 inches high sidewalls. The second section was designed to mesh with the first section in order that the length of the second section could be changed by merely telescoping the first section in or out of the second section. During the course of this run 4 inches of the second section was overlapped with the first section. Also the second section was perforated with l/l6 inch holes on 7/64 inch centers for a 30 percent open area.

Four air knives were positioned 4 inches above the upper horizontal surface of the second section and were spaced apart 4 inches center to center. The air knives were operated with 50 psig air. It is noted that the length of the second section was longer than that needed to accommodate the four air knives on 4 inch centers; however, at the time said section was fabricated it was not known the exact length that would be required.

An electric eye was positioned at the inlet of the second section to detect the presence or absence of the tow plug. Two-speed feed rolls were employed subsequent to the cooling element with the electric eye determining the speed of the feed rolls. The tow leaving the second section was cooled from about l90F to F.

The tow cooled by the above-described apparatus was immediately cut into staple. The staple had excellent crimp and crimp retention and was a marked improvement over staple produced where a conventional J box was employed in lieu of the above-described cooling element.

What is claimed is:

, l. A method for cooling a tow of heated crimped synthetic filaments comprising, in combination: passing said tow through a first zone and a second zone; re-

stricting the movement of said tow in said first zone; cooling said tow in said first zone essentially by natural convection while said tow experiences near zero tension to a temperature such that moderate tension can be applied to the tow in said second zone without impairing the crimp retention of the tow; and cooling said tow in said second zone by forced convection while tensioning said tow sufficiently to elongate said crimped tow but not to remove the crimp in said tow.

2. The method of claim 1 wherein said crimped tow is crimped by a stuffer crimper.

3. The method of claim 1 wherein said crimped tow is cooled in said second zone substantially to ambient temperature, and the tow inventory in said first zone is sensed and controlled.

4. The method of claim 3 wherein said tow is polypropylene.

5. The method of claim 1 wherein said tow is selected from the group of polyolefins, polyesters and polyamides.

6. Apparatus for cooling a heated crimped tow of synthetic filaments comprising, in combination:

crimping means; first and second sections, said first section having a surface extending a distance from said crimping means and being positioned for receiving the tow and said second section having a surface which is an extension of, attached to, and extended a distance outwardly from the surface of said first section to receive said tow from said first section, said first section having a surface which is of sufficient length to cool the tow to a temperature such that moderate tension can be applied to the tow in said second section without impairing the crimp retention of the tow;

a weight means to force said tow against said first section, said weight means being fastened to said first section in a manner to prevent horizontal movement and allow vertical movement of said weight means;

a cooling means for contacting said tow with a cooling fluid in said second section; and

withdrawal means positioned subsequent to said second section to remove the tow therefrom.

7. The apparatus of claim 6 wherein the surface of said first section is of sufficient length so as to provide a tow residence time of from about 5 to about seconds in said first section.

8. The apparatus of claim 6 wherein said weight means comprises a rectangular tray and a weight, said rectangular tray having a curved front portion, the weight of said tray being adjusted by utilizing different size weights therein, and said cooling means comprises air knives for passing air through said tow.

9. The apparatus of claim 6 wherein said first and second sections are trough-like structures with the surface of said second section being perforated.

10. The apparatus of claim 6 wherein a photoelectric device is provided near the junction of said first and second sections which is operated in conjunction with said withdrawal means to control the accumulation of said tow in said first section.

11. Apparatus for treating a tow of synthetic filaments comprising, in combination:

first and second sections, said first section having a surface positioned for receiving the tow and said second section having a surface which is an extension of, attached to and extending a distance outwardly from said first section to receive said tow from said first section, said surface of said second section having perforations therein;

a weight means to force said tow against said first section;

air knives for contacting said tow with a cooling fluid in said second section;

a photoelectric device located near the junction of said first and second sections; and

withdrawal means positioned subsequent to said second section and operated in conjunction with said photoelectric device to control the accumulation of said tow in said first section.

12. Apparatus for cooling a heated tow of synthetic filaments comprising, in combination:

first and second sections, said first section having a surface positioned for receiving the tow and said second section having a surface which is an extension of, attached to and extending a distance outwardly from said first section to receive said tow from said first section. said surfaces of said first and second sections being trough-like structures, said surface of said second section having perforations therein;

a weight means to force said tow against said first section, said weight means comprising a rectangular tray and a weight, said rectangular tray having a curved front portion and the weight of said tray being adjusted by utilizing different size weights therein, said weight means being fastened to said first section in a manner to prevent horizontal movement and allow vertical movement of said weight means;

air knives for contacting said tow with a cooling fluid in said second section;

an electric eye located near the junction of said first and second sections; and

withdrawal means positioned subsequent to said second section and operated in conjunction with said electric eye to control the accumulation of said tow in said first section. 

1. A method for cooling a tow of heated crimped synthetic filaments comprising, in combination: passing said tow through a first zone and a second zone; restricting the movement of said tow in said first zone; cooling said tow in said first zone essentially by natural convection while said tow experiences near zero tension to a temperature such that moderate tension can be applied to the tow in said second zone without impairing the crimp retention of the tow; and cooling said tow in said second zone by forced convection while tensioning said tow sufficiently to elongate said crimped tow but not to remove the crimp in said tow.
 2. The method of claim 1 wherein said crimped tow is crimped by a stuffer crimper.
 3. The method of claim 1 wherein said crimped tow is cooled in said second zone substantially to ambient temperature, and the tow inventory in said first zone is sensed and controlled.
 4. The method of claim 3 wherein said tow is polypropylene.
 5. The method of claim 1 wherein said tow is selected from the group of polyolefins, polyesters and polyamides.
 6. Apparatus for cooling a heated crimped tow of synthetic filaments comprising, in combination: crimping means; first and second sections, said first section having a surface extending a distance from said crimping means and being positioned for receiving the tow and sAid second section having a surface which is an extension of, attached to, and extended a distance outwardly from the surface of said first section to receive said tow from said first section, said first section having a surface which is of sufficient length to cool the tow to a temperature such that moderate tension can be applied to the tow in said second section without impairing the crimp retention of the tow; a weight means to force said tow against said first section, said weight means being fastened to said first section in a manner to prevent horizontal movement and allow vertical movement of said weight means; a cooling means for contacting said tow with a cooling fluid in said second section; and withdrawal means positioned subsequent to said second section to remove the tow therefrom.
 7. The apparatus of claim 6 wherein the surface of said first section is of sufficient length so as to provide a tow residence time of from about 5 to about 20 seconds in said first section.
 8. The apparatus of claim 6 wherein said weight means comprises a rectangular tray and a weight, said rectangular tray having a curved front portion, the weight of said tray being adjusted by utilizing different size weights therein, and said cooling means comprises air knives for passing air through said tow.
 9. The apparatus of claim 6 wherein said first and second sections are trough-like structures with the surface of said second section being perforated.
 10. The apparatus of claim 6 wherein a photoelectric device is provided near the junction of said first and second sections which is operated in conjunction with said withdrawal means to control the accumulation of said tow in said first section.
 11. Apparatus for treating a tow of synthetic filaments comprising, in combination: first and second sections, said first section having a surface positioned for receiving the tow and said second section having a surface which is an extension of, attached to and extending a distance outwardly from said first section to receive said tow from said first section, said surface of said second section having perforations therein; a weight means to force said tow against said first section; air knives for contacting said tow with a cooling fluid in said second section; a photoelectric device located near the junction of said first and second sections; and withdrawal means positioned subsequent to said second section and operated in conjunction with said photoelectric device to control the accumulation of said tow in said first section.
 12. Apparatus for cooling a heated tow of synthetic filaments comprising, in combination: first and second sections, said first section having a surface positioned for receiving the tow and said second section having a surface which is an extension of, attached to and extending a distance outwardly from said first section to receive said tow from said first section, said surfaces of said first and second sections being trough-like structures, said surface of said second section having perforations therein; a weight means to force said tow against said first section, said weight means comprising a rectangular tray and a weight, said rectangular tray having a curved front portion and the weight of said tray being adjusted by utilizing different size weights therein, said weight means being fastened to said first section in a manner to prevent horizontal movement and allow vertical movement of said weight means; air knives for contacting said tow with a cooling fluid in said second section; an electric eye located near the junction of said first and second sections; and withdrawal means positioned subsequent to said second section and operated in conjunction with said electric eye to control the accumulation of said tow in said first section. 